In recent miniaturized semiconductor devices, so-called multilayer interconnection structure is used for electrically interconnecting a vast number of semiconductor elements formed on a substrate. In a multilayer interconnection structure, a large number of interlayer insulation films, each burying therein an interconnection pattern, are laminated, and an interconnection pattern of one layer is connected to an interconnection pattern of an adjacent layer or a diffusion region in the substrate via a contact hole formed in the interlayer insulation film.
With such miniaturized semiconductor devices, complex interconnection patterns are formed in the interlayer insulation film in close proximity, and delay of electric signals caused by the parasitic capacitance of the interlayer insulation film becomes a serious problem.
Thus, with the ultra-miniaturized semiconductor devices of these days called submicron devices or sub-quarter micron devices, a copper interconnection pattern is used as the interconnection layer constituting the multilayer interconnection structure, and a F-doped silicon oxide film (SiOF film) having a specific dielectric constant of 3-3.5 is used for the interlayer insulation film in place of conventional silicon oxide film (SiO2 film) having the specific dielectric constant of about 4.
However, there is a limit in the effort of reducing the specific dielectric constant as long as an SiOF film is used. With such an insulation film based on SiO2, it has been difficult to achieve the specific dielectric constant of less than 3.0 as is required by the semiconductor devices of the generation characterized by the design rule of 0.1 μm or later.
Meanwhile there are various materials called low dielectric (low-K) insulation film having a low specific dielectric constant. On the other hand, an interlayer insulation film used for the multilayer interconnection structure is required not only to have a low specific dielectric constant but also high mechanical strength and high stability against thermal anneal processing.
A F-doped carbon (CF) film is a promising material for the low dielectric constant insulation film for use in ultra fast semiconductor devices of the next generation in view of its sufficient mechanical strength and its capability of achieving low specific dielectric constant of 2.5 or less.
Generally, a F-doped carbon film has a chemical formula represented by CnFm. It is reported that such an F-doped carbon film can be formed by a parallel-plate type plasma processing apparatus or an ECR type plasma processing apparatus.
For example, Patent Reference 1 obtains a F-doped carbon film by using a fluorocarbon compound such as CF4, C2F6, C3F8, C4F8, or the like, in a parallel-plate type plasma processing apparatus as a source gas. Further, Patent Reference 2 obtains a F-doped carbon film by using a fluorinated gas such as CF4, C2F6, C3F8, C4F8, or the like, in an ECR-type plasma processing apparatus.
Patent Reference 1
Japanese Laid-Open Patent Application 8-83842
Patent Reference 2
Japanese Laid-Open Patent Application 10-144675